Preventing Oiliness in Salami-Type Dried Sausages at Ambient Temperature

EarthwormExpress — Applied Meat Science

Fat exudation, particle integrity, and the chemistry of keeping a dry sausage dry

By Eben van Tonder and Christa van Tonder-Berger

EarthwormExpress | Origins Global Meats — 2026

Table of Contents

Introduction

Oiliness on the surface and cut face of fermented dried sausages held at ambient temperature is a persistent commercial and technical problem. The defect presents as a visible sheen or actual pooling of liquid fat, and it signals a structural failure within the product. The problem is particularly acute wherever products are sold without continuous refrigeration, as is common across West Africa, large parts of Southern and Central Africa, and informal retail markets in many other regions.

The phenomenon is not fat smearing, which occurs during manufacture. It is a post-manufacture, temperature-driven migration of liquid fat fractions from within the product to the surface or cut face. Understanding why it occurs requires an account of the physical behaviour of pork and beef fat at temperatures above 20 degrees Celsius, and understanding how to prevent it requires an integrated approach to raw material selection, fat handling, matrix formation, drying, and packaging.

This article draws on the Kulmbach research tradition, represented by the Bundesanstalt für Fleischforschung and its successor institution the Max Rubner-Institut, as well as the broader German, Austrian, and American meat science literature. The controls described here apply equally to conventional European salami production and to fermented and dried sausage production in African markets where ambient temperature management is a persistent challenge.

“Fat hardness at 20 to 25 degrees Celsius is a critical selection criterion for dry sausages, because fat that is too soft at these temperatures will inevitably release liquid oil fractions during ambient display.”
After Schiffner, Habermeier, and Oppel (1988)¹

1. The Physical Basis: Fat Melting Behaviour

Pork backfat and jowl fat are not uniform substances. They are complex mixtures of triglycerides, each with its own melting point, and the overall melting behaviour of any fat depot reflects the proportional composition of these triglycerides.² The iodine value of a fat sample is the most practical indicator of the proportion of unsaturated fatty acids present. Unsaturated fatty acids introduce kinks in the fatty acid chain, which disrupt the ordered crystalline packing of triglycerides and lower the effective melting range of the fat.³

Wirth (1988), in his foundational technical work produced at Kulmbach, documented that backfat with an iodine value above 70 is consistently associated with pronounced fat exudation at temperatures above 20 degrees Celsius.⁴ This is because a significant fraction of the triglycerides in such fat are already liquid at typical ambient retail temperatures of 22 to 30 degrees Celsius. Zebu and other Bos indicus subcutaneous fats have a somewhat higher saturated fatty acid proportion than European pork backfat, which offers a modest natural advantage in warmer climates, but this advantage is not sufficient on its own to prevent oiliness at 28 to 35 degrees Celsius.

The physics are straightforward. Fat that is solid at 15 degrees Celsius may begin to yield liquid oil fractions at 22 degrees Celsius because the lower-melting triglyceride fractions cross their transition temperature. These liquid fractions are mobile. They migrate along the boundary between fat particles and the protein matrix, and they accumulate at the product surface or at cut faces where they are visible as oiliness.

2. The Role of Fat Particle Structure

In salami-type products, fat is incorporated as discrete, cold-cut particles. The structural objective of correct processing is to maintain these particles as a defined, encapsulated particulate phase suspended within and bound to the lean protein-salt matrix. Three conditions must hold for this structure to remain stable through the shelf life of the product.

First, the fat must be sufficiently cold and hard at the time of cutting and mixing. Second, the protein matrix must form an adequate binding film around each fat particle through myofibrillar protein extraction and gelation during fermentation and drying. Third, the fat must not undergo oxidative degradation to a degree that disrupts its internal crystalline structure.⁵

Buckenhüskes (1993) and the German Fleischwirtschaft literature confirm that fat particles which lose structural cohesion with the surrounding protein matrix become mobile liquid reservoirs when ambient temperatures rise to or above 22 to 28 degrees Celsius.⁶ The protein film around each fat particle is therefore not merely a textural feature. It is a functional barrier against liquid fat migration. Its formation depends on adequate ionic strength during mixing and on the progressive drying and protein consolidation that occurs during the fermentation and drying stages.

3. Practical Preventive Measures

3.1 Fat Selection

Fat should have an iodine value below 60, and preferably below 55. Neck fat and jowl fat are generally too soft and unsaturated for salami-type products intended for ambient sale. Hard pork backfat from the rump or shoulder region is preferred. Fat must be frozen to minus 10 to minus 18 degrees Celsius before cutting. Repeated freeze-thaw cycling must be avoided, because each freeze-thaw cycle disrupts the triglyceride crystalline structure and lowers the effective melting point of the fat depot.⁴

3.2 Cutting Temperature

Fat should be cut at minus 8 to minus 12 degrees Celsius. Cutting at these temperatures maintains sharp particle edges and prevents smearing of fat into the lean matrix. Smeared fat is not encapsulated by protein because it presents no defined surface for protein adsorption, and therefore it exudes freely when the product warms above the fat melting range.^4,7

3.3 Protein Matrix Integrity

Adequate extraction of salt-soluble proteins from the lean phase is essential to fat particle encapsulation. Myofibrillar proteins, particularly myosin, adsorb onto fat particle surfaces and form a cohesive binding film during drying. Hamm (1986) documented this mechanism in detail, demonstrating that the functional properties of the myofibrillar system are directly dependent on salt concentration and that insufficient ionic strength leads to inadequate protein extraction and therefore to poorly bound fat particles.⁷ Salt levels of 25 to 32 grams per kilogram of finished formulation support adequate ionic strength for myosin solubilisation under normal processing conditions.

3.4 Water Activity and the Drying Curve

Controlled drying to a water activity below 0.92, and ideally to 0.88 to 0.85 for shelf-stable ambient products, consolidates the protein matrix and physically immobilises fat particles within a tighter, drier structure. Products dried only to water activity values of 0.93 to 0.95 retain a looser, more hydrated matrix that provides significantly less physical resistance to fat particle movement when the product is warmed.⁸ The drying curve must therefore be designed with the intended ambient display temperature in mind. Products destined for warm ambient retail require more aggressive drying targets than products held under refrigeration.

3.5 The Role of Smoking

Traditional cold-smoking contributes a surface layer of phenolic compounds, aldehydes, and organic acids that polymerises to form a semi-impermeable surface film. This film retards outward migration of liquid fat fractions from the product surface.⁹ Smoking therefore addresses surface oiliness. However, it does not prevent internal fat liquefaction or the migration of liquid fat to cut faces, and it is not a substitute for correct fat selection and matrix formation.

3.6 Antioxidant Protection

Lipid oxidation of unsaturated fatty acids produces peroxides and secondary aldehydes that degrade triglyceride crystalline structure. Products sold at ambient temperature and exposed to light and oxygen undergo progressive oxidation, and oxidised fat phases lose structural cohesion more readily than intact fat.³ Sodium ascorbate at 500 milligrams per kilogram, rosemary extract standardised for carnosic acid content, or mixed tocopherols retard this oxidative degradation and thereby help maintain fat particle integrity over the display period.

3.7 Casing Selection

Natural casings and collagen casings are permeable to moisture vapour and allow continued slow drying and equilibration with ambient humidity. Impermeable plastic casings trap moisture and can create a humid microenvironment beneath the casing that softens the outer fat ring and promotes fat exudation at the surface. For ambient display, permeable natural or collagen casings are preferred because they allow ongoing moisture equilibration rather than trapping condensed moisture that would otherwise solubilise surface fat fractions.

3.8 Display Temperature

The most direct intervention available is the control of ambient display temperature. Even products manufactured to optimal specification will exude some liquid fat at 30 to 35 degrees Celsius because triglyceride melting is a physical property of the fat, not a manufacturing defect. Where refrigeration is unavailable, as in many West African retail environments, the fat selection, cutting temperature, matrix formation, and drying curve controls described above become correspondingly more important. They do not eliminate the underlying physics, but they raise the threshold temperature at which visible oiliness occurs and reduce the rate of oil migration once that threshold is crossed.^4,6

4. Summary of Controls

Variable	Target Specification	Mechanism
Fat iodine value	Below 60, ideally below 55	Higher saturated fraction raises the melting range and reduces liquid fat yield at ambient temperatures
Fat cutting temperature	Minus 8 to minus 12 degrees Celsius	Prevents smearing and maintains defined particle surfaces for protein adsorption
Finished water activity	0.85 to 0.90 for ambient product	Consolidates protein matrix and physically immobilises fat particles
Salt level	25 to 32 g/kg formulation	Supports myosin extraction and formation of the protein encapsulation film
Antioxidant	500 mg/kg sodium ascorbate or equivalent	Retards oxidative disruption of fat crystalline structure
Casing type	Natural or collagen casing, permeable	Prevents moisture trapping at the fat-surface interface
Display temperature	Below 20 degrees Celsius where possible	Keeps fat below the liquid transition range of dominant triglyceride fractions

Conclusion

Oiliness in salami-type dried sausages at ambient temperature is a fat physics problem as much as it is a formulation or processing problem. The liquid fat fractions in any commercial fat depot will migrate when the product reaches and exceeds the melting range of those fractions. The manufacturer’s task is to select fats with a higher inherent melting range, to ensure that fat particles are correctly encapsulated within the myofibrillar protein matrix, to dry the product to a water activity that consolidates the matrix, and to deploy antioxidant and smoking controls that retard the secondary degradation of fat structure over the shelf life of the product.

In warm ambient markets, none of these controls alone is sufficient. They must be applied together as an integrated system. The manufacturer who addresses only one variable while neglecting the others will continue to see oiliness at retail. The manufacturer who addresses all variables systematically will produce a product that is substantially more stable at ambient temperatures, even if the underlying physics of fat melting can never be entirely overcome.

The discipline required is the same discipline that the Kulmbach tradition and the German master butcher tradition have applied for decades. It is demanding in its detail. However, it is entirely achievable with commercially available raw materials and standard processing equipment, and it is essential for any fermented and dried sausage product that must travel and sell across warm-climate markets.

References

Schiffner, E., Habermeier, J., and Oppel, K. (1988). Technologie der Fleischverarbeitung. VEB Fachbuchverlag, Leipzig. pp. 214–231.
Gunstone, F.D., Harwood, J.L., and Dijkstra, A.J., eds. (2007). The Lipid Handbook. 3rd edition. CRC Press, Boca Raton. Chapter 6: Composition and Properties of Edible Fats.
Nawar, W.W. (1996). Lipids. In Food Chemistry, 3rd edition, edited by Fennema, O.R. Marcel Dekker, New York. pp. 225–319.
Wirth, F. (1988). Technologie der Brühwurst und Rohwurst. Bundesanstalt für Fleischforschung, Kulmbach. pp. 178–209.
Cassens, R.G. (1994). Meat Preservation: Preventing Losses and Assuring Safety. Food and Nutrition Press, Trumbull. pp. 42–58.
Buckenhüskes, H.J. (1993). Selection criteria for lactic acid bacteria to be used as starter cultures for various food commodities. FEMS Microbiology Reviews, 12(1–3), pp. 253–271.
Hamm, R. (1986). Functional properties of the myofibrillar system and their measurements. In Muscle as Food, edited by Bechtel, P.J. Academic Press, New York. pp. 135–199.
Lücke, F.K. (1994). Fermented meat products. Food Research International, 27(3), pp. 299–307.
Tompkin, R.B. (2007). Smoking of meat products. In Handbook of Fermented Meat and Poultry, edited by Toldrá, F. Blackwell Publishing, Oxford. pp. 189–198.